Commercial wireless communications networks consist of cellular phone or radio services supported by an array of short range transmission towers each providing coverage for an area or “cell,” with an array of adjacent cells forming a network coverage area. More recently, a number of wireless service providers have begun combining satellite dish and terrestrial wireless technologies to augment the range and throughput of their signal to offer higher-bandwidth fixed wireless services such as interactive television (ITV) and high-speed Internet access. Each of these architectures requires a centralized network infrastructure to send and receive signals throughout the region and connect them to a land-based backbone.
Several technologies have been employed in digital wireless systems. These include Time Division Multiple Access (TDMA), in which users share the same frequency by transmitting and receiving only during short “time slots.” A number of improvements have been made over the years to TDMA, including the introduction of the Global System for Mobile Communications (GSM), which allowed faster bit rates and the use of more natural-sounding voice compression algorithms. Another improvement was frequency hopping (in which the call actually changes frequency quite often during a transmission) which randomized the effects of co-channel interference and reduced multi-path interference. Recently, a new compression algorithm was added to GSM called the “Enhanced Full Rate CODEC” which can produce voice quality rivaling that of wire line telephones.
Another technology employed in digital wireless systems is Code Division Multiple Access (CDMA), in which instead of dividing up the users of a channel by time slots, everyone transmits at the same time and is separated by their encoding scheme. The military has used this type of technology for its communications, and most satellites communicate this way as well. Instead of using a narrow channel and modulating signals onto a fixed carrier, CDMA uses a very wide channel and spread the bits out using a “spreading algorithm.” If one were to listen to such a transmission, it would sound like background noise.
Another wireless telecommunications system is the Personal Communications Service (PSC). This network utilizes a cell architecture that is similar to digital cellular systems using TDMA, although PCS cells are generally smaller.
A more recent wireless development is Multichannel Multipoint Distribution Service (MMDS), a fixed (i.e., using a non-mobile mounted dish) wireless access solution capable of providing both broadband data and voice connectivity. MMDS has been used for video broadcast services such as wireless cable and pay-per-view. Wireless broadband solutions are in part an attempt to solve the familiar last mile problem—it is extremely costly to string the last individual length of cable to every home in a region.
Wireless technologies have most recently been developed to extend the reach of Local Area Networks (LANs) to mobile devices throughout a building or corporate campus. These Wireless Local Area Networks (WLANs) allow users of wireless mobile devices including laptop/notebook computers and handheld device computers such as Personal Digital Assistants (PDAs) to connect to their LAN. Wireless LANs use electromagnetic waves (radio or infrared) to communicate information from one point to another without any physical connection. Thus, WLANs provide all the functionality of wired LANs, but without the physical constraints of the wire itself (as well as hubs, bridges, routers, and other infrastructure).
WLAN systems typically include wireless Network Interface Cards (NICs) that are installed in the various PDAs and laptops seeking connectivity, and Wireless Access Points (WAPs), which are fixed transmitter/receiver (transceiver) devices that are connected to the wired network by standard Ethernet cable. The WAPs function as miniature cellular towers, coordinating network traffic between the local network and a limited number of NIC-enabled devices. In other words, LANs can be thought of as consisting of many expensive and sophisticated elements (hubs, bridges, routers, etc.), and the user's NIC is simply an inexpensive onramp which connects the user to the LAN.
Over the last several years, WLANs have gained strong popularity in a number of vertical markets where mobile use is required, including the health care, retail, manufacturing, warehousing, and academic arenas. These industries have profited from the productivity gains of using handheld terminals and notebook computers to transmit real-time information to centralized hosts for processing. Increasingly, WLANs are becoming widely recognized as general-purpose connectivity alternatives for a broad range of business customers.
While these and other technologies represent significant advances in the development of wireless networks, there remain a number of problem areas. One such problem for cellular networks is that they require cellular towers, line-of-sight placement, and/or the purchase of a spectrum license. The process of planning, building, maintaining, and upgrading cellular towers and infrastructure is extremely costly. Cellular tower arrays are very costly to build because property rights must be secured for each tower or antenna location, which can be particularly expensive and difficult to arrange in cities, in addition to the costs of material and labor for each tower in the array.
Additionally, in planning to build out an array of towers to establish a coverage area for future users, it is impossible for the service provider to know in advance exactly how many customers will be using the network and where those customers will be. Because wireless networks allow for user mobility, this problem is magnified. The population of Manhattan more than triples each day as people from upstate New York, Long Island, the various other boroughs, and New Jersey commute into the city to work. However, the current cellular infrastructure is fixed and cannot respond to these fluctuating needs.
A related drawback is the scalability problem inherent in existing cellular, cable-modem, and ADSL (telephone co.) services. When more and more users access these networks, whether as new subscribers located within a cell or as mobile users passing through a cell, the network becomes flooded and cannot handle the volume being demanded. This can cause the speed of the network to slow down to a crawl. And because the network has a fixed capacity, at some point it will simply crash.
Furthermore, conventional wireless networks are not easily upgradable. Given the rapid rate of technological advance, the time currently required for new technologies to be integrated into the telecommunications infrastructure and offered to customers is no longer acceptable, so the existing model of upfront capitalization, installation, and amortization is simply not sustainable. By the time telecommunications and cable companies actually dig up their existing plant and get new equipment installed into the ground or onto the poles, it has already become obsolete (or soon will be). Therefore, cellular companies must continually upgrade thousands of towers and antennae in order to provide new types of services to compete and keep their customers.
Another problem with known wireless systems is signal degradation resulting from interference caused by objects and metals in the surrounding environment. The current approach for solving this problem is simply to use more power to force the signal through a crowded environment. This is a crude and inefficient solution to the problem.
With regards to conventional WLAN systems, a significant drawback is their limited range. WLAN technologies offer services that are far more localized than cellular, with effective operating distances typically in the 250 to 2500 foot range. Also, WLAN manufacturers generally offer only very low-end, low-power WAP hardware that supports only a dozen or so users per WAP. Therefore, users are effectively limited to short ranges beyond which they cannot use their PDA or laptop to access their LAN.
Moreover, a major problem with conventional wired systems that has not been overcome by current wireless systems is the last mile problem. Because of the high costs of stringing the last length of cable to every home in a region, telecommunications and cable television companies have only been able to provide access to broadband services to a limited number of homes and offices.
Accordingly, what is needed but not found in the prior art is a cost-effective wireless telecommunications architecture that operates without the need for costly cellular towers or infrastructure. Additionally, there is a need for such a network architecture that is infinitely scalable, broadband-capable, nondeterministic, and mobile-responsive to changes in user location. Furthermore, there is a need for a wireless device that can be used to connect to such a network as well as to WLANs and other networks.